Constructional material



Patented May 14, 1946 UNITED STATES PATENT orrics con s'raucrromr. MATERIAL Henry Dreyfus and William Walker, London, and James Henry Rooney, Spondon, near Derby, England; said Walker and said Rooney assignon to British Celanese Limited, London, England, a company of Great Britain; Claude Bonard administrator of said Henry Dreyfus, deceased No Drawing. Application September 14, 1943, Se-

rlal No. 502,304. In Great Britain August 17,

1942 I 8 Claims.

Tins invention relates to constructional materials and particularly to a new kind of constructional material suitable for use in the building trade.

The constructional material of the invention vcomprises particles or wood bonded together by means of a minor proportion of cellulose acetate or other water resistant thermoplastic hinder to may be coated with dopes having a basis of cellulose acetate, ellulose acetate stearate or ethyl cellulose and containing a plasticiser for the cellulose derivative, in solution in a volatile solvent.

The coating may be effected by steeping the aturcs but not at ordinary temperatures.) Thus when cellulose acetate is used as the binder ace tone or dioxane or methanol or ethanol, in amount about equal to that of the cellulose acetate may be incorporated in the moulding powder or in the mixture or this powder with the wood particles, and evaporated on before the moulding operation. The mixture may be formed into a coherent material in the same way as the coated particles referred to above, e. g. at pressures of. l50

. to 1000 or 1500 lbs. per square inch.

The wood employed may be in the form of wood-flour, sawdust, shavings, chips or the like. In general, better results qua water resistance of the product are obtained the smaller the wood particles. Homogeneity in the wood is of considerable advantage from the point of view of obtaining uniformity in the product. Thus it is preierred to work with wood-flour, sawdust,v chips or shavings of a single kind or wood. The wood or broad leaved trees may be employed and close grained woods of this kind, for example, oak, teak, birch and beech are very suitable. The wood of coniferous trees, e. g. the various kinds of wood particles in the .dope, draining them and 28 pine and fir, may also be used. From the point drying them, e. g. at about 80 C. The ratio of cellulose acetate or other binder to wood may vary largely, for instance from about 1:5 or even less, e. g. 1:7, up to about 4:5. Very useful prodnets are obtained for example when the ratio is between about 1:4 and about 3:5, e. g., between 1:3 and 1:2. The coated particles may be formed into a coherent sheet or slab of material by a moulding operation carried out atla temperature of about 150 C. and a pressure of 150-500 lbs. per square inch. In this way a material oi' specific gravity about lis obtained. By employing a higher pressure for instance 750 or 1000 to 1500 lbs. per square inch, 9. denser and stronger material can be obtained, for instance one having a speciflcgravity between about 1.0 and 1.5. The moulding may be carried out in a multi-platen steam heated press.

which is a solvent therefor at elevated temper- 55 of view of water resistance in the product, the use of resinous woods isoi advantage. Valuable results have been obtained with a wood containing ether-soluble matter to the extent or 2%02' less and moisture content oi 10% or less.

As indicated above, suitable binders include cellulose acetate, cellulose acetate-stearate and ethyl cellulose. Where water resistance in the product is of importance it is preferable to employ a highly water-resistant binder. For this purpose ethyl cellulose, cellulose acetate-stearate and cellulose acetate containing combined acetic acid in excess of about 55%. for instance 56 to 58 or 59%, are even more suitable than the more common cellulose acetate or lower acetic acid content. Other thermoplastic artiflcial film-forming substances of high water resistance that can be employed include other esters of cellulose, for example cellulose propionate, cellulose butyrate, cellulose acetate-propionate, cellulose acetatebutyrate and cellulose acetate-nitrate and other ethers of cellulose in which the ether radicle contains at least 2 carbon atoms, for example benzyl cellulose and ethyl hexyl cellulose. Water resistant polymerised unsaturated synthetic resins, for example polystyrenes, polyvinyl acetatechloride, polymethyl .methacrylate and other polyvinyl compounds can also be employed. 0 It is desirable that the material of the invention should contain in addition to the thermophate. Aromatic phosphates such as triphenyl phosphate and tricresyl phosphate, although of excellent water-resistance are preferably not employed as the sole plasticiser for cellulose acetate on account of their very limited solvent power therefor. They may, however, be employed in admixture with plasticlsers of higher solvent power for cellulose acetate for example, triacetin or dimethyl phthalate.

Suitable solvents for cellulose acetate when employing a dope with which to coat the wood particles include in addition to the solvents mentioned above, methylene ethylene ether, mixtures of methylene chloride or ethylene chloride with methanol or ethanol and of acetone, ethanol and benzene.

The following examples in which all the parts are by weight illustrate the invention:

Example 1 A moulding powder is made of the following composition:

Parts Cellulose acetate of acetyl value about 53% (calculated as acetic acid) Dimethylphthalate 28 Tri-phenylphosphate 9 This powder is mixed. in a Werner-Pileiderer mixer with three times its weight of a Columbian pine sawdust which passes a sieve of meshes to the inch and is retained by one of l0 meshes to the inch. I

The mixture is pressed, in a multi-platen press i for minutes under a pressure of 1,000 to 1,500

lbs. per square inch, to form sheets about A; of an inch in thickness.

In this way a sheet material or specific gravity of about 1.2, suitable for use as a building board and capable of being sawed, drilled or nailed can .be obtained.

Example 2 A moulding powder of the following compositionismade:

Parts Cellulose acetate as specified in Example i 1 Di-methoxyphthalate 1 Example 3 A moulding powder is made of the following composition:

' Parts Ethyl cellulose 01' ethoxy content about 29%-- 5 Di-ethylphthalate 1 This powder is mixed with twice its weight or wood sawdust and moulded as described in Exof the fatty acid concerned).

aeo ore ample 1. The boards formed are of higher watereresistance than those oi Examples 1 and 2.

Example I! The process is carried out as described in Example 3 but substituting for the ethyl cellulose a cellulose acetate-stearate of acetyl value 39.9 and stearoyi value 29 (both calculated as percentages Somewhat lower pressures can beemployed in moulding the mix of this example owing to the greater plasticity of the acetate-stearate compared with the cellulose derivatives of the previous examples. 'lhus a good compact board can be obtained by moulding for 30 minutes at 500 to 1,000 lbs. per square inch. The method of this example enables product of still higher water-resistance than those of the preceding examples to be obtained.

Example 5 A dope of the following composition is formed:

' Parts Cellulose acetate as specified in Example 1... l0

Tri-acetin l0 Acetone 25 Ethanbl l0 Benzene l5 The process is carried out as in Example 5 except that a dope of the following composition is employed:

Parts Cellulose acetate of acetyl value 56-59% (calculated as acetic acid) 10 Dimethyl phthalate or diallyl phthalate 2 to 5 Methyl acetate In this way a product of higher water-resistance than that of Example 5 can be obtained.

Example 7 The process is carried out as in Examples 5 or I 6 but substituting for the sawdust an equal weight oi wood shavings. In this way .boards are formed having a pleasant pattern-effect. The products 0! this example are in general less water-resistant and or lower tenacity than those of the previous examples in which sawdust is employed.

Example 8 The process is carried out as in Examples 5 or 7 but employing a dope of the following composition:

Example 9 The process is carried out as in Example 5 or 7 but using a dope of the following composition:

Parts Cellulose acetate-stearate of acetyl value 24.1 and stearoyl value 54.5 (calculated as percentages oi the fatty acid) 9 Dl-ethylphthalate 2 Acetone 70 n Benzene 8 I using a cellulose derivative binder, thermoplastic synthetic resins may be employed in place of the cellulose derivatives of the above examples. Thus dopes or moulding powders having a basis of polymethyl methacrylate can be employed. The products obtained, however, are in general of considerably lower impact strength than when cellulose derivatives are employed. Polyvinyl acetate may also be employed instead of the cellulose derivatives, but in this case the products are softer and less resistant to heat.

The material-of-theinvention may usefully be produced in thei'onn of sheets from $2" or less up to /z" or more in thickness and having sides several feet in length. Such sheets may, for example, be used, mounted on suitable frames, in forming the walls and roofs of hutsbams and like buildings. They may also be used for interior panelling and as ceiling boards, black-out screens and the like. They may be formed with plane perpendicular edges or with edges bevelled, rabbeted, tonglled and grooved or otherwise shaped so that adjacent sheets interlock. Th material of the invention may also, by the .use of suitably shaped moulds, be produced in forms suitable for use as frame members for windows or doors, picture rails, hand-rails, skirting boards, cornices and other interior fittings commonly made or wood. Furniture components can also be formed of the material. The material can further be produced in the form 01' thick sheets, slabs or blocks from which short scantlings, planks and boards can be cut. Where ornamental materials are required, patterned dies may be used in the moulding operation.

applied, for example by brushing or spraying methods; or the materials may be given a coating of a partially polymerised thermosetting synthetic resin which may then be further polymerised to the insoluble condition on the material. The material for example, may be coated with a solution of an intermediate condensation product of formaldehyde with urea, a phenol, or like poly-.- functional monomer and may then be baked to insoiubilise the condensation product. The msterial can also be given a metallic coating, for

example by spraying methods.

Laminated materials maybe built up by uniting two or more sheets of the material or the invention by means of a suitable adhesive, e. a.

cellulose acetate or other thermoplastic flimforming polymer or a thermosetting synthetic in a volatile solvent or in powder form, union being then eilected by a hot pressing operation.

Having described our invention, what we desire to secure by Letters Patent is:

1. A molded structural material having a specific gravity between about 0.1 and 0.5 and being suitable for use in paneling, said material consisting of wood chips closely bonded together into a coherent mass b means of a binder consisting solely of a substantially solvent-free plasticized substance selected from the class consisting of water-insoluble organic esters and ethers of cellulose, at most 4 parts of said substance being present per 5 parts 01' wood chips, the parts being by weight.

2. A molded structural material having a speciiic gravity between about 0.1 and 0.5 and being suitable for use in paneling, said materials consisting of wood chips closely bonded together intoa coherent mass by means of a binder consisting solely of a substantially solvent-free plasticized cellulose acetate, at most 4 parts of said substance being present per 5 parts of wood chips, the parts being by weight.

3. A molded structural material having a specific gravity between about 0.1 and 0.5 and being suitable for use in paneling, said material consisting oi wood chips closely bonded to ether into a coherent mass by means of a binder consisting solely of a substantially solvent-free plas-. ticized ethyl cellulose, at most 4 parts of said substance being present per 5 parts 01' wood chips, the parts being by weight.

4. A molded structural material having a speciflc gravity between about 0.1 and 0.5 and being suitable for use in paneling, said material consisting of wood chips closely bonded together into a coherent mass by means of a binder consisting solely of a substantially solvent-free plasticized cellulose acetate stearate, at most 4 parts of said substance being present per 5 parts of wood chips, the parts being by weight.

5. Process for the production or a structural material suitable for use in paneling, which com prises closely bonding together into a coherent mass having a specific gravity of 1.0 to 1.5, at a temperature of about 150 C. and a pressure of 150 to 1500 lbs. per square inch, and in the substantial absence of a solvent, wood chips coated with a binder consisting solely of a plasticized substance selected from the class consisting of water-insoluble organic esters and ethers or cellulose, at most 4 parts of said substance being present per 5 parts of wood chips, the parts being by weight.

6. Process for the production of a structural material suitable for use in paneling, which comprlses closely bonding together into a coherent mass having a specific gravity or 1.0 to 1.5, at a temperature of about 150 C. and a pressure of 150 to 1500 lbs. per square inch, and in the substantial absence of a solvent, wood chips coated with a binder consisting solely of a plasticized cellulose acetate, at most 4 parts of said substance being present per 5 parts or wood chips, the parts being by weight. g

7. Process for the production of a structural material suitable for use in paneling, which comprises closely bonding together into a coherent /mass having a specific, gravity of 1.0 to 1.5, at a temperature of about C. and a pressure oi 150 to 1500 lbs. per square inch, and in the substantial absence or a solvent, wood chips coated with a binder consisting solely oi a plasticised resin. The adhesive may be applied in solution 7 ethyl cellulose, at most 4 parts of said substance being present per 5 parts of wood chips, the parts being by weight.

8. Process for the production of a structural material suitable for use in paneling, which com prises closely bonding together into a coherent mass having a specific gravity of 1.0 to 1.5, at a temperature of about 150 C. and a, pressure 0! 150 to 1500 lbs. per square inch, and in the sub- 5 the parts being by weight.

HENR

stantial absence of a. solvent, wood chips coated with a binder consisting solely of a plasticized cellulose acetate stearate, at most 4 parts of said substance being present per 5 parts of wood chips,

Y DREYF'US. WILLIAM WALKER. JAMES HENRY RODNEY. 

